Hi Bobby,
I had the same problem about a week ago when I did an oatmeal stout. I also heard that you don't want to go above an RA of 250 for the mash. I targeted 220 and my mash pH came out high actually, 5.6 (but I was using the cheap strips, so I take that with a grain of salt). I built my profile from distilled water, and here's what I did:
Mash Water Profile:
2.68 gallons total (100% distilled), 1 tsp. Chalk, 1/8 tsp. Calcium Chloride, 1/8 tsp. Epsom Salt, and 3/4 tsp. Baking Soda
Calcium - 83ppm
Magnesium - 5ppm
Sodium - 89ppm
Chloride - 20ppm
Sulfate - 22ppm
RA: 219
SRM: 23-28
Sparge with distilled water.
Salts added to the boil:
2 tsp. Chalk, 1/8 tsp. Calcium Chloride, 1/4 tsp. Epsom Salt, and 5/8 tsp. Baking Soda
Total Water Profile (6.15 gallons):
Calcium - 103ppm
Magnesium - 7ppm
Sodium - 71ppm
Chloride - 18ppm
Sulfate - 28ppm
RA: 191
SRM: 21-26
I was also concerned about the high sodium level and that I didn't have enough sulfate (Palmer says 50ppm is the minimum). It's difficult, because with the sodium relatively high, you want to keep the sulfate low to prevent a harsh bitterness.
I'm glad to say that I took a gravity sample last night after 9 days of fermentation. The beer was awesome. The hop presence was low (possibly due to the low sulfate level), but that was how I intended it to be per the recipe. No harsh bitterness at all.
Just wanted to give you my experience.